Body armor has been around for a long time. In general, the desire is to make the body armor as flexible, light and as breathable as possible and still withstand the impact of incoming projectiles or other lethal instrumentalities. In recent years, some body armor has been made from a woven and/or a non-woven fabric comprising filaments of very high molecular weight polymers, suitably polyolefins, such as polyethylene or high molecular weight polypropylene, and/or aramid polymers. These fabrics are sold commercially under the names "Spectra", "Protera" and "Kevlar". One of the newer anti-ballistic filaments is sold under the trade name "Zylon", which comprises a PBO resin.
It is also known in this art to create an antiballistic fabric by coating a woven layer of anti-ballistic cloth, such as an aramid (Kevlar), with a resorcinol-formaldehyde latex in a quantity sufficient to fill the interstices of the woven cloth and to coat the individual filaments/yarns of the woven fabric. This product is very stiff and brittle. Because the interstices are completely filled this fabric does not breath to any appreciable extent. Reference is here made to U.S. Pat. No. 4,522,871.
Reference is here made to U.S. Pat. No. 4,737,402 in the name of Harpell et al. which has an excellent discussion of the chemical nature of some of these filaments that have been found to be well suited to use in protective fabrics of the general type to which this invention is directed. The entire substance of this patent is incorporated herein by reference. The object of these composite fabrics is to cause the incoming ballistic projectile to expend its energy breaking the filaments of the fabric, and therefore to lose its energy and its impetus to penetrate into the body being protected by the fabric. It has previously been found that composite fabrics made up of woven fabrics and non-woven disposed in layers have a better combination of stopping power and light weight than do fabrics made of the same material in either woven or non-woven form in a non-layered assembly for the same weight of fibers.
It had recently been found, see U.S. Pat. No. 5,395,671, the entire substance of which is incorporated herein by reference, that a certain construction of a composite fabric, comprising multi-layers of high molecular weight woven and non-woven fabrics, respectively assembled in a particular manner, had unusual ability to stop the penetration of even very high energy projectiles, such as a very high energy projectile issuing from a 0.44 magnum bullet. This composite fabric construction also has the ability to stop a projectile from a 9 mm bullet. This composite fabric comprised at least two independent layers of material.
In this composite fabric, the two layers of material, each composed of a plurality of sub-layers, were not attached to each other. The "incoming" side of the fabric, that is the side of the composite fabric that is facing in the direction from which the projectile threat is incoming, is suitably made of multiple sub-layers or plies of non-woven fabric, comprising very high molecular weight polymer filaments that are usually individually disposed unidirectionally. The structure of the sub-plies of the non-woven fabric is often a plurality of layers of such unidirectionally disposed fibers, with successive layers assembled crosswise to each other. Thus, the unidirection of the filaments or fibers of these multiple layers can be considered to be disposed at angles to each other. For example, if the direction of the fibers of the first layer are considered to be at an angle of 0.degree., the fibers of the next layer might be considered to be disposed at an angle of 90.degree. with respect to direction of the first filaments. In the next layer, the filaments might be laid substantially parallel to the filaments of the first layer and would thus have a 0.degree. orientation, and so forth. Of course, other sequences of filament angular displacements are appropriate as well, such as for example 45.degree. angular displacements. Thus a series of four (4) successive layers might be angularly offset as follows: 0.degree., 45.degree., 90.degree., 45.degree., and then back to 0.degree., whereupon the series pattern starts again. The layers could also be angularly offset by increments of 30.degree. to make up a five (5) layer repeating pattern.
The "skin" side of the fabric, that is the side of the fabric disposed away from the incoming direction of the projectile, and disposed toward the object in need of protection, is suitably made up of multiple sub-plies of woven fabric comprising high molecular weight polymer filaments woven together in any chosen weave pattern. These woven filaments, or threads, can have substantially the same chemical composition as the filaments that make up the non-woven layers. It is also possible for the woven and the non-woven filaments of a given composite fabric to be made of different polymers. The specific filaments of either the woven or the non-woven sub-plies, or both may be made of mixed filaments, that is filaments of different chemical composition and/or different molecular weights and/or different denier and/or different filament cross section configuration. It is also possible to reverse the woven fabric and place it on the incoming side, with the non-woven fabric being, disposed on the skin side.
In one, known, particularly good construction of body armor, the sub-layers or plies of the woven fabric are quilted together. It has been found that a composite fabric with an excellent combination of projectile stopping power, flexibility and light weight has been achieved with a combination of a woven fabric side and a non-woven fabric side, where two criteria hold true. A plurality of the woven sub-plies are quilted together and form the skin side of the fabric, and a plurality of sub-criteria of the invention of the above referred to '671 patent because it is the combination of these two elements that has been found to cause the final composite fabric to have its unusual and unexpectedly effective stopping power coupled with unusual light weight.
Another recent development in this field is disclosed in U.S. Pat. No. 5,343,796. This patent describes a composite fabric protective system comprising an incoming, or face, layer that has as its purpose to slow the velocity and reduce the energy of the incoming projectile so that the second, skin layer, then can stop this now lower velocity/lower energy projectile. According to this patent, the first, or incoming layer (referred to in the patent as the "face layer" is a pliable, cut resistant fibrous layer; and the second, or "skin layer" is a pliable impact/ballistic energy absorbing fibrous layer. The '796 patent also alleges that the first and second layers can be reversed with the energy absorbing layer being the face layer and the cut resistant layer being the second layer. Three layer sandwich composite fabric systems are also disclosed where the third layer is like the first layer.
Many different fibers and fiber combinations are disclosed in this reference and the entirety of this reference is therefore incorporated herein by reference. Any of these fibers and fiber combinations, as well as other fibers and fiber combinations can be used in the practice of the instant invention.
The composite fabric of the '671 patent is an excellent protective material from which excellent protective garments are made. However, because this composite fabric was intended to stop a 240 grain 44 magnum bullet traveling at an impact velocity of 1450 feet per second, the fabric is necessarily fairly heavy. That is, it has a higher than desired areal density. It is made up many layers of both woven and non-woven sub-layers that have been assembled as aforesaid. Because this fabric has to have this exceptional stopping power, it is necessarily made up of these multiple layers of woven and non-woven fabrics. The intended use of this fabric, that is to stop a 0.44 magnum projectile, requires that there be a substantial number of sub-layers of non-woven fabric in this composite. The use of such multiple layers of non-woven fabrics, made of high molecular weight polymer filaments, makes the fabric reasonably stiff and therefore less than ultimately comfortable to the wearer. Further, the lowest areal density that has been achieved with this composite fabric configuration while retaining the ability to stop a 0.44 magnum projectile, traveling at an impact velocity of 1,450 feet per second, has been about 0.95 to 1.15 pounds per square foot.
The need for serious impact protection was answered by the fabric of the '671 patent, but at these very low areal densities, protection was afforded only for lower energy projectiles. This special fabric structure could be assembled at the set forth low areal density range that was considered to be quite low at the time.
Stiff protective clothing, particularly such clothing that has a very tight weave or disposition of filaments, and even more particularly such clothing that comprises layers of non-woven fabric, has a degree of discomfort to the wearer in direct proportion to its areal density and its flexibility. For the same polymer filaments, it is axiomatic that the higher the areal density of the fabric, the greater is the stopping power of the fabric. In higher areal density fabrics, there are more filaments in the way of the incoming projectile. It is also a fact that, for fabrics made up of the same filaments, the higher the areal density of a fabric, the stiffer is the fabric because it has more filaments and therefore progressively fewer void spaces. Similarly, the tighter the weave of the fabric, or the closer together are the filaments of the non-woven fabric, the higher will be the areal density and the stiffer will be the fabric.
In modern protective clothing, a balance must be struck between the stopping power of the anti-ballistic portion of the garment or fabric and the degree of discomfort the wearer is willing to put up with. If the fabric has too few filaments, or if the molecular weight and/or denier of the filaments making up the fabric is too low, or if the fabric is too thin, even though the fabric will have greater wearability, there will be insufficient ballistic protection afforded the wearer, and the fabric will not have achieved its purpose.
The direction in which this art is going is consistent with the direction in which the power of guns is going. That is, with time, the impact velocity and penetrating power of ballistic projectiles has continued to increase, and therefore, the stopping power of protective garments has also increased. This has been accomplished by using stronger and higher molecular weight filaments, by increasing the weight and stiffness of the fabric, and by assembling the fabric from different elements and in different configurations, such as using both woven and non-woven fabrics, which provide different, and cumulatively superior effective kinds of stopping power. However, it is also desired to lighten the fabric, make it less uncomfortable to the wearer, and still have it stop high energy incoming ballistic projectiles, like that issuing from a 0.44 magnum bullet.
U.S. Pat. No. 5,185,195 discloses a penetration resistant article which is made up of plural layers of ballistic fabrics that have been stitched together in a certain pattern. The purpose of this construction is to stop knife and pick penetration. Specifically, this patent discloses joining together at least two plies of flexible fibrous materials. The key element of this patent is the stitching together of these two or more layers of flexible fabric such that the rows of stitches that are adjacent each other are separated by less than about 1/8 of an inch. In this disclosure, the stitching pattern is critical, and the proximity of the lines of stitching is an essential part of the invention disclosed therein as it is alleged that it is this stitching pattern that creates the knife and pick stopping power that is the reason for the composite fabric that has been disclosed. It is important to note that the securing means, the stitching or the like, is not disclosed to cover the substantial entirety of the fabric sub-layers that are being attached to each other. The distinctness of the several lines of securing of the two sub-layers of flexible fabric together is disclosed as being important to maintain the flexibility of the composite sub-fabric, and therefore the flexibility of the entire final fabric that is made up of a plurality of sub-assemblies of fabrics, some joined together and others not.
The product of the '195 patent is said to be useful in preventing the penetration of knife and pick attack. However, in practice, it has been found that the proximity of the stitching securing means does not accomplish the intended purpose. In fact, because of the tightness of the securing of the two sub-fabrics together, knife penetration is not substantially retarded at all. A sharp knife or pick penetrates this composite fabric almost as easily as it does fabrics of the same sub-fabric construction that have not been stitched together.